What is Crigler-Najjar syndrome?

Crigler-Najjar syndrome (CNS) is a very rare genetic condition. It happens in around 1 in every million births. It affects males and females in equal numbers.

Crigler-Najjar syndrome causes long-term jaundice in newborn babies. It happens when the liver can’t get rid of a substance called bilirubin. Bilirubin is made by the body when red blood cells break down. In Crigler-Najjar syndrome, bilirubin collects in the blood. This causes a range of symptoms and complications.

There are two types of Crigler-Najjar syndrome:

type 1 and type 2

Each one has a different level of severity. It is very important to find out if a child has type 1 or type 2 CNS.

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What causes Crigler-Najjar syndrome?

Crigler-Najjar syndrome is a genetic condition. This means it is caused by changes in a person’s DNA. Genetic conditions are passed from one or both parents to their children. Crigler Najjar syndrome is an autosomal recessive condition. This means that both parents are carriers of the change (mutation) and can pass it on to their child.

In healthy babies, the liver uses a protein called UDPGT to turn bilirubin into bile. The body does this by changing it from unconjugated bilirubin to conjugated bilirubin. Conjugated bilirubin helps the body digest fats and then passes out in the poo.

Unconjugated bilirubin has not been processed by the liver. It is very toxic to the body.

Conjugated bilirubin has been processed by the liver. It is not toxic to the body.

Babies with Crigler-Najjar syndrome are missing one or both of the genes that tell the body how to make the UDPGT protein. Without the protein, the liver can’t process unconjugated bilirubin. It builds up in the body and this is known as hyperbilirubinemia. It causes a range of symptoms and complications. The main symptom is jaundice. Jaundice is when the skin or the whites of the eyes turn yellow.

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How is Crigler-Najjar syndrome diagnosed?

Severe jaundice that appears in the first days of life may lead to suspicion of Crigler-Najjar syndrome. Tests used to help confirm the diagnosis may include:

• physical examination
• liver blood tests – this will include a split bilirubin test, which checks the amount of conjugated and unconjugated bilirubin in the body
• wee (urine) test
• genetic testing

A drug called phenobarbital can be used to help find out if a child has type 1 or type 2 Crigler-Najjar syndrome. This drug reduces bilirubin levels in type 2 but makes no difference in type 1.

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Useful words

Bilirubin – a natural waste product caused by the breakdown of old red blood cells

Genetic condition – any medical condition caused by a problem with someone’s genes

Jaundice – a condition where the skin or eyes turn yellow